JP3756486B2 - Contact failure detection method and apparatus for electric power equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to detection of poor contact of electric power equipment used in power transmission and distribution facilities. The present invention is applied to, for example, detecting a contact failure between a road break elbow and a junction and a contact failure between a movable electrode and a fixed electrode of a multi-circuit switch.
[0002]
[Prior art]
Conventionally, as a method for detecting a contact failure occurring at a connection portion of a power device, a method for detecting heat generated due to the contact failure or a method using X-ray transmission imaging is known. For example, Non-Patent Document 1 describes a contact failure detection method using a thermal image by a thermo label or thermography. Patent Document 1 describes a method in which a shape memory needle whose shape changes due to heat is attached to a connecting portion, and a contact failure is detected by electric discharge generated when the shape memory needle is deformed.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-64422 (FIG. 1)
[Non-Patent Document 1]
Makishi City, “Latest Practical Equipment Diagnosis Technology”, General Technology Center, 1988, p. 869-875
[0004]
[Problems to be solved by the invention]
However, the cause of heat generation of the members may be load current amount, slight difference in contact resistance of each connection part, ambient environment, etc. in addition to poor contact. It cannot be said that there is always a poor contact. Therefore, it is qualitative to detect a contact failure in a target part from information such as a thermal image, and skill for judgment is required.
[0005]
Further, in the method using the shape memory needle, it is difficult to set the temperature at which the shape memory needle is deformed. That is, if the temperature setting is high, the detection of contact failure is delayed and preventive maintenance cannot be performed, and if the temperature setting is low, the shape memory needle is deformed due to heat generation other than the contact failure.
[0006]
Furthermore, the method using X-ray transmission imaging requires shielding around the imaging region, the detection device is large, and installation and removal are complicated, and it is difficult to install the detection device depending on the power equipment. There is no versatility. In addition, the determination of poor contact based on an X-ray transmission image must be qualitative and requires skill.
[0007]
In view of the problem in the conventional contact failure detection of a power device, the present invention has an object to provide a highly reliable detection method capable of detecting a contact failure of a power device with high accuracy. Another object of the present invention is to provide a quantitative contact failure detection method that can be easily executed at a site where power equipment is installed and does not require skill.
[0008]
  A first aspect of the present invention is a power device.Near the connectionAn ultrasonic sensor is placed on the power device while AC power is being supplied to the power device.SaidWith ultrasonic sensorIn the vicinity of the connectionBased on the ultrasonic wave detected and detected by the ultrasonic sensor,SaidPower equipmentIn the connectionProvided is a contact failure detection method for a power device, which detects a contact failure.
[0009]
When a contact failure occurs in a connecting portion of a power device such as a load break elbow and a junction or a movable electrode and a fixed electrode of a multi-circuit switch, discharge occurs, and as a result, ultrasonic waves are generated. A contact failure can be detected by detecting this ultrasonic wave with an ultrasonic sensor.
[0010]
  Specifically, the generation period of the periodic component of the ultrasonic wave is compared with a power supply frequency that is the frequency of the AC power supplied to the power device, and the generation period of the ultrasonic component is the power supply frequency.Or the generation period of the periodic component of the ultrasonic wave is the power frequency.If it is within a predetermined range twice (for example, ± 10%), it is determined that a contact failure has occurred.
[0011]
In the present invention, since contact failure is detected using ultrasonic waves generated only due to the occurrence of discharge at a contact failure location, for example, compared with the case where heat generation due to contact failure is used, the accuracy and reliability are high. High contact failure can be detected. Moreover, since it is determined whether or not the ultrasonic wave is caused by poor contact by comparing the periodic component of the ultrasonic wave and the power supply frequency, for example, compared with the case of using a thermal image or an X-ray transmission image, It is possible to detect a contact failure with accuracy, and quantitative evaluation without skill is possible. Furthermore, a large-scale device such as shielding of the ultrasonic sensor placement location is not necessary, and contact failure can be easily detected at the site where the power equipment is installed. Furthermore, if the ultrasonic sensor can be arranged, the type of electric power device to be detected is not particularly limited, and therefore versatility is high.
[0012]
The periodic component of the ultrasonic wave may be detected from the time-amplitude waveform of the ultrasonic wave detected by the ultrasonic sensor, but in order to improve the detection accuracy of the periodic component, a short-time Fourier is applied to the time-amplitude waveform. It is preferable to perform time-frequency analysis such as transformation, wavelet transformation, Wigner distribution function, etc., and to detect periodic components based on the time-frequency analysis. Further, the periodic component may be detected by applying a fast Fourier transform to the waveform of the ultrasonic wave detected by the ultrasonic sensor or its envelope detection waveform.
[0013]
Since the ultrasonic wave is attenuated as it propagates in the electric power device, the ultrasonic wave intensity is stronger as the installation position of the ultrasonic sensor is closer to the position of the contact failure where the discharge is generated. Therefore, in order to improve the accuracy and reliability of contact failure detection, ultrasonic detection during the supply of AC power to the power device by the ultrasonic sensor is repeated at a plurality of locations of the power device, and the ultrasonic waves at the plurality of locations are detected. When the intensity of the periodic component is changing, it is preferable to determine that the periodic component is due to discharge resulting from poor contact.
[0014]
Further, since the intensity of the periodic component of the ultrasonic wave has a correlation with the distance from the contact failure occurrence position to the ultrasonic sensor as described above, the alternating current to the power equipment by the ultrasonic sensor at a plurality of locations of the power equipment. The detection of the ultrasonic wave during power supply is repeated, and the location of occurrence of poor contact in the power device can be determined based on the intensity difference of the periodic component of the ultrasonic wave at each detection position.
[0015]
As an alternative, since the arrival time of the ultrasonic wave generated due to the contact failure is earlier as it is closer to the occurrence point of the contact failure, the ultrasonic sensors are arranged at a plurality of locations of the power device, respectively, Based on the temporal relationship of the generation of the periodic component of the ultrasonic wave detected by the sensor, it is possible to determine the occurrence location of the contact failure in the power device.
[0016]
  The second aspect of the present invention is an electric power device.Near the connectionUltrasonic waves generated during AC power supply to power equipmentIn the vicinity of the connectionBased on the ultrasonic sensor to detect and the ultrasonic wave detected by the ultrasonic sensor,SaidPower equipmentIn the connectionProvided is a contact failure detection device for a power device, comprising a processing unit that detects contact failure.
[0017]
The processing unit includes a periodic component detection unit that detects a periodic component of the ultrasonic wave detected by the ultrasonic sensor, a generation cycle of the periodic component of the ultrasonic wave detected by the periodic component detection unit, and the power device. If the generation frequency of the periodic component of the ultrasonic wave is within the predetermined range of the power supply frequency or twice that, the contact failure has occurred. It is preferable to provide the determination part to determine.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Next, the present invention will be described in detail with reference to embodiments shown in the drawings.
[0019]
(First embodiment)
As shown in FIG. 1, the contact failure apparatus according to the embodiment of the present invention includes an ultrasonic sensor 10, a preamplifier 11, a filter 12, an amplifier 13, and a processing unit 14. The detection signal of the ultrasonic sensor 10 is sent to the processing unit 14 through the preamplifier 11, the filter 12, and the amplifier 13.
[0020]
The ultrasonic sensor 10 is, for example, a piezoelectric element type ultrasonic sensor, and is installed on the surface of the power device 17 that is a detection target of contact failure via a contact medium 16 such as silicon grease. However, the ultrasonic sensor 10 is not limited to the piezoelectric element type, and may be any sensor that can detect ultrasonic waves with good sensitivity. The contact medium 16 is used to reduce transmission loss of ultrasonic waves at the contact portion between the ultrasonic sensor 10 and the power device 17 and to ensure insulation between the power device and the contact failure detection device.
[0021]
The preamplifier 11 amplifies a weak detection signal output from the ultrasonic sensor 10 in order to reduce the influence of noise. The filter 12 is for removing disturbance noise and electrical noise included in the detection signal of the ultrasonic sensor 10. Further, the filter 12 can adjust the low-pass filter cutoff frequency and the high-pass filter cutoff frequency, and allows only the optimum band to pass according to the dominant frequency of the ultrasonic wave at the time of occurrence of discharge due to poor contact. The amplifier 13 amplifies the detection signal in order to improve the S / N ratio in the processing unit 14.
[0022]
As shown in FIG. 2, the preamplifier 11 may be built in the ultrasonic sensor 10. In FIG. 2, reference numeral 26 denotes an ultrasonic detection element such as a piezoelectric element, and the preamplifier 11 is accommodated in the housing 10 a of the ultrasonic sensor 10 together with the element 26. Since the preamplifier 11 is built in, the length of the signal line between the element 26 and the preamplifier 11 can be greatly shortened, so that the introduction of inductive noise can be prevented.
[0023]
Based on the detection signal input from the ultrasonic sensor 10, the processing unit 14 detects a contact failure that has occurred in the connection unit of the power device 17.
[0024]
Although the electric power apparatus which is the detection target of a contact failure is not specifically limited, For example, the road break elbow 20 and the junction 21 which are shown in FIG. 3 become a detection target. The load break elbow 20 includes a compression terminal 24 at the end of the cable conductor 23 exposed from the cable insulator 22, and a screw portion on the proximal end side of the pin contact 26 is attached to the compression terminal 24. The proximal end sides of the compression terminal 24 and the pin contact 26 are covered with a semiconductive layer and an insulating layer. The tip end side of the pin contact 26 protrudes into the insertion hole 20a for inserting the load break elbow 20, and an arc extinguishing rod 27 is provided at the tip. On the other hand, the junction 21 includes a tulip contact 28 that contacts the pin contact 26 on the road break elbow 20 side. A looper 29 is disposed between the piston 31 disposed on the proximal end side of the tulip contact 28 and the aluminum housing 30. A current flows from the cable conductor 23 to the aluminum housing 30 through the compression terminal 24, the pin contact 26, the tulip contact 28, the piston 31, and the louver 29. In the load break elbow 20 and the junction 21, the connection portion C 1 between the compression terminal 24 and the pin contact 26, the connection portion C 2 between the pin contact 26 and the tip contact 28, and the connection portion C 3 (louver 29) between the piston 31 and the aluminum housing 30. The occurrence of contact failure in () is a detection target.
[0025]
Another example of the detection target is a multi-circuit switch 40 shown in FIGS. 4 and 5. The multi-circuit switch 40 includes a plurality of (for example, five circuits) switches each including a fixed electrode portion 61 and a movable electrode portion 62. The fixed electrode portion 61 includes a terminal 65a connected to the bus 64 routed in the gantry 63, and a terminal 65b on the cable 67 side. On the other hand, the movable electrode portion 62 includes a pair of terminals 68a and 68b corresponding to the terminals 65a and 65b on the bus 64 side and the cable 67 side, respectively, and these terminals 68a and 68b are connected to each other. As shown in FIG. 5, when the movable electrode portion 62 is in the lowered position, the terminals 68a and 68b of the movable electrode portion 62 are connected to the terminals 65a and 65b of the fixed electrode portion 61, and the circuit composed of the bus 64 and the cable 67 is closed. Is done. On the other hand, when the movable electrode portion 62 is in the raised position and the terminals 68a and 68b of the movable electrode portion 62 are disconnected from the terminals 65a and 65b of the fixed electrode portion 61, the circuit is opened. In the multi-circuit switch 40, the occurrence of contact failure at the connection portions C4 and C5 of the terminals 65a and 65b of the fixed electrode portion 61 and the terminals 68a and 68b of the movable electrode portion 62 is a detection target.
[0026]
  Other power devices that can be detected include cable terminals., ElectricThere are motives, switchboards, control panels, various switches, relays, etc.
[0027]
The processing unit 14 detects the occurrence of contact failure based on the detection signal received from the ultrasonic sensor 10. The processing unit 14 is connected to a monitor 51, an input device (not shown), and the like so that the operator operates the contact failure detection device.
[0028]
The contact failure detection device can be configured by combining various analog circuits and digital circuits, and various devices including measurement devices. For example, the processing unit 14 including the filter 12, the amplifier 13, and the monitor 51 can be configured by an ultrasonic waveform discriminator and a digital oscilloscope.
[0029]
A signal line 52 connecting the ultrasonic sensor 10 and the preamplifier 11 is inserted through the ferrite core 53. This is because inductive noise whose cause is not necessarily clear may be mixed between the ultrasonic sensor 10 and the preamplifier 11, so that the influence of this type of noise is reduced.
[0030]
Next, a contact failure detection method using this contact failure detection device will be described. First, the ultrasonic sensor 10 is disposed on the surface of the power device 17 via the contact medium 16. Next, ultrasonic waves are detected by the ultrasonic sensor 10 in a state where AC power is supplied to the power equipment, that is, in a live line state.
[0031]
The detection signal of the ultrasonic sensor 10 is sent to the processing unit 14 via the preamplifier 11, the filter 12, and the amplifier 13. At this time, the signal line 52 between the ultrasonic sensor 10 and the preamplifier 11 is inserted into the ferrite core 53, or the preamplifier 11 is built in the ultrasonic sensor 10, so that the ultrasonic sensor 10 and the preamplifier 11 are connected. It is possible to improve the S / N ratio by preventing the induction noise from being mixed.
[0032]
Referring to FIG. 6, the processing unit 14 has an amplitude threshold L that is sufficiently larger than the noise amplitude L1 of thermal noise, disturbance noise, etc. of the power equipment._THIs preset. The amplitude L1 of the periodic component of the detection signal of the ultrasonic sensor 10 is the amplitude threshold L_THIn the case where the frequency exceeds the value, the processing unit 14 determines that the periodic component detected by the ultrasonic sensor 10 is caused by the discharge of the connection portion, and that a contact failure has occurred in the connection portion.
[0033]
In this way, since contact failure is detected using ultrasonic waves generated by discharge at a contact failure location, for example, compared to the case where heat generation at a contact failure location is used, detection of contact failure with high accuracy and high reliability can be performed. It can be carried out. Further, since a large-scale device such as shielding of the installation location of the ultrasonic sensor 10 is not required, it is possible to easily detect a contact failure at the site where the power equipment is installed. Furthermore, it is possible to detect a contact failure simply because there is no need to detect a voltage pulse or a current pulse.
[0034]
By repeating the measurement with the ultrasonic sensor 10 at a plurality of locations of the power equipment, it is possible to improve detection accuracy and determine the location of contact failure. Hereinafter, this point will be described by taking as an example a case where the detection targets are the road break elbow 20 and the junction 21 shown in FIG.
[0035]
As shown in FIGS. 7A and 7B, measurement positions P1 to P4 are set at four locations on the surface of the road break elbow 20. Among these measurement positions P1 to P4, the measurement position P2 is disposed closest to the connection portion C1 (see FIG. 3) between the compression terminal 24 and the pin contact 25, and the measurement positions P1, P3, and P4 are arranged in this order. Thus, the distance from the connection portion C1 is increased. In addition, the measurement position P1 is disposed closest to the connection portion C2 between the pin contact 25 and the tulip contact 28, and the distance from the connection portion C2 is increased in the order of the measurement positions P2, P3 and the measurement position P4. . Further, the measurement position P3 is disposed closest to the connection portion C3 between the piston 31 and the aluminum housing 30, and the distance from the connection portion C3 is increased in the order of the measurement positions P1, P2, and P4. The detection of ultrasonic waves is repeated at the measurement positions P1 to P4 in the live line state. One ultrasonic sensor 10 may be used to detect ultrasonic waves at each of the measurement positions P1 to P4, or ultrasonic sensors 10 may be disposed at the respective measurement positions P1 to P4 to detect ultrasonic waves. You may go. Moreover, you may perform the detection in each measurement position P1-P4 simultaneously.
[0036]
Since the ultrasonic wave is attenuated as it propagates through the electrode device, the closer the installation positions P1 to P4 of the ultrasonic sensor 10 are to the connection portions C1 and C2 where the poor contact occurs, the amplitude of the periodic component of the ultrasonic wave Becomes larger. Therefore, when the waveform shown in FIG. 8 is detected at each of the measurement positions P1 to P4, the amplitude threshold L at the measurement positions P1 and P2._THPeriod components Z1 and Z2 having an amplitude exceeding 1 are detected, and the amplitudes are different between the measurement position P1 and the measurement position P2. Therefore, it can be determined that the periodic components Z1 and Z2 are caused by discharge at a contact failure location. Further, since the amplitude of the periodic component Z2 at the measurement position P2 is larger than the amplitude of the periodic component Z1 at the measurement position P1, and the magnitude of the amplitude is in the order of the measurement positions P2, P1, P3, P4, the contact failure is caused. It can be determined that the generated portion is the connection portion C1 between the compression terminal 24 and the pin contact 25 closest to the measurement position P2. Similarly, when the waveform shown in FIG. 9 is detected at each of the measurement positions P1 to P4, the amplitudes of the periodic components Z1 and Z2 are different at the measurement positions P1 and P2, so that it can be determined that the discharge is caused by a contact failure location. . Further, since the amplitude of the periodic component Z1 at the measurement position P1 is larger than the amplitude of the periodic component Z2 at the measurement position P2, and the amplitudes are in the order of the measurement positions P1, P2, P3, P4, contact failure occurs. It can be determined that the connection portion C2 between the pin contact 25 and the tulip contact 28 closest to the measurement position P1. When a contact failure occurs at the connection portion C3 between the piston 31 and the aluminum housing 30, the magnitude of the amplitude of the ultrasonic wave at each measurement position is in the order of P3, P1, P2, and P4.
[0037]
Based on the arrival time of the ultrasonic wave, it is possible to determine a contact failure location. Hereinafter, this point will be described. As shown in FIGS. 7A and 7B, the ultrasonic sensors 10 are respectively installed at the four measurement positions P1 to P4 of the road break elbow 20, and an alternating current is being supplied to the load break elbow 40 and the junction 41. Measure the ultrasound. When the waveform of the ultrasonic wave at each measurement position P1 to P4 is shown in FIG. 10, the threshold amplitude L at each measurement position P1 to P4._THThe time when the amplitude exceeding is detected is td1 to td4, respectively. When the supply of AC power is started, the arrival time of the ultrasonic wave generated due to the contact failure is earlier as it is closer to the location where the contact failure occurs. When the detection times td1 to td4 are compared, the threshold amplitude L in the order of the measurement positions P2, P1, P3, P4._THUltrasound with an amplitude greater than is detected. Therefore, it can be determined that the measurement position P <b> 2 is closest to the discharge occurrence point due to the contact failure, and the contact failure is generated at the connection portion C <b> 1 between the compression terminal 24 and the pin contact 25.
[0038]
(Second Embodiment)
In the contact failure detection device according to the second embodiment of the present invention shown in FIG. 11, the processing unit 14 includes a periodic component detection unit 18 that detects a periodic component of the ultrasonic wave from the detection signal of the ultrasonic sensor 10, and a periodic component detection. The periodic component detected by the unit 18 is compared with the frequency (power supply frequency) of the AC power supplied to the power device, and whether the periodic component of the ultrasonic wave is due to a discharge generated due to poor contact or not. And a determination unit 19 for determining whether or not.
[0039]
The detection signal of the ultrasonic sensor 10 includes noise such as thermal noise and disturbance noise of electric power equipment, and the periodic component resulting from discharge due to poor contact is pulse-like, so that it was detected by the ultrasonic sensor 10. The proportion of this periodic component in the entire waveform is very small. Therefore, when the S / N ratio is low, it is difficult for the periodic component detector 18 to directly detect the periodic component from the waveform of the ultrasonic wave or the detected waveform thereof. In addition, since the normal fast Fourier transform obtains the frequency spectrum of the entire waveform, instantaneous changes are averaged within the number of data points, making it difficult to catch. If the S / N ratio is low, the accuracy is high. It is difficult to detect periodic components.
[0040]
Therefore, in the present embodiment, time-frequency analysis is adopted as a frequency analysis method used by the periodic component detection unit 18 in order to detect the periodic component and its generation period with high accuracy. In this time-frequency analysis, an ultrasonic waveform is divided in the time axis direction, and a frequency spectrum is detected for each divided time section.
[0041]
An example of the time-frequency analysis is a short-time Fourier transform. In the short-time Fourier transform, a window is set by dividing an ultrasonic waveform in the time axis direction, and the fast Fourier transform is applied to each window by shifting the window little by little on the time axis. If the window width is set to be sufficiently shorter than the ultrasonic waveform, only a part of the original waveform will be present. By applying the Fast Fourier Transform to this waveform, the frequency spectrum at the moment can be obtained. It is possible to extract changes in a short time. Other time-frequency analysis includes wavelet transform and Wigner distribution function.
[0042]
When the S / N ratio is large, as described in the first embodiment, the periodic component detection unit 18 can detect the periodic component directly from the waveform of the ultrasonic wave or the detected waveform thereof. In addition, when the S / N ratio is large, frequency analysis may be performed by performing fast Fourier transform on the waveform of the ultrasonic wave or its envelope detection, thereby detecting the periodic component.
[0043]
The ultrasonic periodic component detected by the periodic component detection unit 18 is input to the determination unit 19. The determination unit 19 compares the generation period of the detected periodic component of the ultrasonic wave with the power supply frequency, and determines whether or not discharge has occurred due to poor contact. The determination principle will be described with reference to FIG.
[0044]
FIG. 12A shows a voltage V acting in the vicinity of two members causing poor contact when an AC voltage is supplied to a power device._a(Two-dot chain line) and the voltage V acting between these members_b(Solid line). Voltage V_aThis frequency is the same as the frequency of the AC voltage (power supply frequency) supplied to the power equipment.
[0045]
  Voltage V until time t1_aIncreases, so the voltage V_bIs positive spark voltage + V_thAnd discharge occurs as shown in FIG. When discharge occurs, a reverse electric field is formed between the two members, and the voltage V_bInstantaneously drops to almost 0V. Voltage V from time t1_aWhen starts to drop, the voltageV _b Will also drop with the spark voltage -V_thAnd discharge occurs. This discharge causes the voltage V_bMomentarily returns to 0V, but the voltage V_aAs the voltage drops, the voltage V_bAgain, the spark voltage -V_thAnd discharge occurs. Since these two discharges occur at an extremely short time interval, they can be regarded as one discharge PD. Voltage V from time t3_aWhen the voltage starts to rise, the voltage V_bRises accordingly, and spark voltage + V_thAnd discharge occurs. This discharge causes the voltage V_bInstantaneously drops to almost 0V, but the voltage V_aAs the voltage rises, the voltage V_bWill also rise, so the spark voltage is again -V_thAnd discharge occurs. Since these discharges are also generated at extremely short time intervals, they can be regarded as a single discharge PD.
[0046]
As a result of the above process being repeated, the voltage V_aThe discharge PD is repeatedly generated in the vicinity where the value changes from the zero cross, and the generation cycle is the voltage V_a, Ie, twice the power frequency. Further, depending on the situation, the discharge PD may occur only in either the positive or negative phase of the voltage Va. In this case, the generation period of the discharge PD is the same as the power supply frequency. Therefore, if the ultrasonic wave detected by the ultrasonic sensor 10 includes a periodic component and the periodic component has a generation cycle that is the same as or nearly twice the power supply frequency, the periodic component is caused by poor contact. It can be considered that this is due to the discharge.
[0047]
FIGS. 13 and 14 schematically show an example in which frequency analysis is performed by applying a short-time Fourier transform to an ultrasonic waveform in the periodic component detection unit 18. FIG. 13 shows a case where a periodic component caused by a discharge having the same generation cycle (50 Hz) as the power supply frequency (50 Hz) is included, and FIG. 14 is caused by a discharge having a generation cycle (100 Hz) twice the power supply frequency. This shows a case where a periodic component is included.
[0048]
As shown in FIGS. 13A and 14A, the periodic component X is buried in the noise Y in the original waveform of the ultrasonic wave. When a short-time Fourier transform is applied to this waveform, a periodic component X appears in the frequency spectrum as shown in FIGS. 13 (B) and 14 (B). Then, as shown in FIGS. 13C and 14C, the generation period of the periodic component is detected from the temporal change of the spectrum intensity.
[0049]
The generation period of the ultrasonic periodic component detected by the periodic component detection unit 18 as described above is sent to the determination unit 19. The determination unit 19 compares the generation period of the periodic component with the power supply frequency, and if the periodic component is the same as the power supply frequency or within a predetermined range with respect to twice the power supply frequency, the periodic component detected by the periodic component detection unit 18 Is determined to be caused by discharge. For example, when the power supply frequency is 50 Hz, the determination unit 19 causes the periodic component of the ultrasonic wave to be generated if the generation cycle of the ultrasonic periodic component detected by the periodic component detection unit 18 is within a predetermined range of 50 Hz or 100 Hz. Therefore, it is determined that the discharge is generated at the poor contact portion. The predetermined range is set in consideration of measurement error, error accompanying frequency analysis, and the like. For example, the predetermined range is set to a range of ± 10% that is the same as or twice the power supply frequency. In the example of FIG. 13, the frequency of the periodic component is the same as the power supply frequency, and in the example of FIG. 14, the frequency of the periodic component periodic component is twice the power supply frequency. Therefore, in any of the examples, the determination unit 19 determines that discharge has occurred due to poor contact.
[0050]
In the present embodiment, as described above, it is determined whether the ultrasonic wave is caused by poor contact by comparing the periodic component of the ultrasonic wave and the power supply frequency. For example, a thermal image or an X-ray transmission image is obtained. Compared with the case of using, it is possible to detect a contact failure with high accuracy, and it is possible to perform quantitative evaluation with high reliability without requiring skill. In particular, by detecting a periodic component by time-frequency analysis, detection with higher accuracy becomes possible.
[0051]
Since other configurations and operations of the second embodiment are the same as those of the first embodiment, the same elements are denoted by the same reference numerals and description thereof is omitted.
[0052]
The present invention is not limited to the above-described embodiment, and various modifications can be made. For example, when the detection target is a multi-circuit switch, the ultrasonic sensors 10 may be arranged at six measurement positions P1 'to P6' as shown in FIG.
[0053]
【The invention's effect】
As is clear from the above description, in the method and apparatus of the present invention, since contact failure is detected using ultrasonic waves accompanying discharge at a contact failure location, for example, when heat generated due to contact failure is used. In comparison, highly accurate and reliable detection of contact failure can be realized. Moreover, since it is determined whether or not the ultrasonic wave is caused by poor contact by comparing the periodic component of the ultrasonic wave and the power supply frequency, for example, compared with the case of using a thermal image or an X-ray transmission image, It is possible to detect a contact failure with accuracy, and a highly reliable quantitative evaluation is possible without requiring skill. Furthermore, since a large-scale device such as shielding of the ultrasonic sensor placement location is not necessary, it is possible to easily detect contact failure at the site where the power equipment is installed. Furthermore, if the ultrasonic sensor can be arranged, the type of electric power device to be detected is not particularly limited, and therefore versatility is high.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a contact failure detection apparatus according to a first embodiment of the present invention.
FIG. 2 is a schematic diagram showing an ultrasonic sensor incorporating a preamplifier.
FIG. 3 is a cross-sectional view showing a connection state between a load break elbow and a junction.
4A and 4B show a multi-circuit switch, in which FIG. 4A is a partial front view, and FIG. 4B is a partial plan view.
FIG. 5 is a cross-sectional view taken along line VV in FIG.
FIG. 6 is a graph showing the relationship between the amplitude of ultrasonic waves and noise caused by poor contact.
7A and 7B show an arrangement of ultrasonic sensors attached to a load break elbow, where FIG. 7A is a side view and FIG. 7B is a front view.
FIG. 8 is a graph showing an example of an ultrasonic measurement waveform detected by ultrasonic sensors arranged at a plurality of locations.
FIG. 9 is a graph showing another example of an ultrasonic measurement waveform detected by ultrasonic sensors arranged at a plurality of locations.
FIG. 10 is a graph showing an example of an ultrasonic measurement waveform detected simultaneously by a plurality of ultrasonic sensors.
FIG. 11 is a schematic view showing a contact failure detection device according to a second embodiment of the present invention.
12A is a graph showing a relationship between a voltage acting in the vicinity of a connecting portion of a power device and a voltage acting on a connecting portion in which a contact failure occurs, and FIG. 12B is a discharge corresponding to FIG. It is a graph which shows a pulse waveform.
FIG. 13 shows an example of detection of a periodic component (50 Hz) of an ultrasonic wave by short-time Fourier transform, (A) is a graph showing a measured waveform, and (B) is a concept showing a frequency spectrum obtained by short-time Fourier transform. FIG. 4C is a graph showing the relationship between the spectral intensity of the periodic component and time.
FIG. 14 shows an example of detection of a periodic component (100 Hz) of an ultrasonic wave by short-time Fourier transform, (A) is a graph showing a measured waveform, and (B) is a concept showing a frequency spectrum obtained by short-time Fourier transform. FIG. 4C is a graph showing the relationship between the spectral intensity of a specific periodic component and time.
[Explanation of symbols]
10 Ultrasonic sensor
10a housing
11 Preamplifier
12 Filter
13 Amplifier
14 Processing unit
16 Contact medium
17 Electric power equipment
18 Periodic component detector
19 Judgment part
20 Road break elbow
20a insertion hole
21 junction
22 Cable insulation
23 Cable conductor
24 Compression terminal
25 pin contact
27 Arc extinguishing rod
28 Tulip contact
29 louvers
30 Aluminum housing
31 piston
40 Multi-circuit switch
51 Monitor
52 signal lines
53 Ferrite core
61 Fixed electrode part
62 Movable electrode part
63 frame
64 busbar
65a, 65b terminals
67 cable
68a, 68b terminal

Claims (8)

An ultrasonic sensor is placed near the connection part of the power equipment,
Wherein detecting the ultrasound in the vicinity of the connecting portion by ultrasonic sensor during AC power supply to the electrical equipment,
On the basis of the ultrasonic wave detected by the ultrasonic sensor, for detecting a contact failure in the connection of the power device, contact failure detection method of the power equipment. Compare the generation period of the periodic component of the ultrasonic wave and the power supply frequency that is the frequency of the AC power supplied to the power device,
If the generation period of the periodic component of the ultrasonic wave is within a predetermined range of the power supply frequency , or if the generation period of the periodic component of the ultrasonic wave is within a predetermined range of twice the power supply frequency , contact failure occurs. The contact failure detection method according to claim 1, wherein the contact failure detection method is determined.   The contact failure detection method according to claim 2, wherein the periodic component is detected by time-frequency analysis of the detected ultrasonic wave.   When the ultrasonic sensor is repeatedly detecting the ultrasonic power during the supply of AC power to the power device by the ultrasonic sensor at a plurality of locations of the power device, and the intensity of the periodic component of the ultrasound at the plurality of locations is changing, the cycle The contact failure detection method according to claim 2, wherein the component is determined to be caused by contact failure.   In the power device, the ultrasonic sensor repeats the detection of the ultrasonic wave during the supply of AC power to the power device at a plurality of locations of the power device, and based on the intensity difference of the periodic component of the ultrasonic wave at each detection position. The contact failure detection method according to claim 2, wherein the occurrence location of the contact failure is determined. The ultrasonic sensors are respectively disposed at a plurality of locations of the power device,
The contact failure according to claim 2 or 3, wherein a location of occurrence of contact failure in the electric power device is determined based on a temporal relationship between generation of periodic components of ultrasonic waves detected by individual ultrasonic sensors. Detection method. An ultrasonic sensor that is disposed in the vicinity of the connection portion of the power device and detects an ultrasonic wave that is generated during the supply of AC power to the power device in the vicinity of the connection portion ;
A contact failure detection device for a power device, comprising: a processing unit that detects a contact failure at the connection portion of the power device based on an ultrasonic wave detected by the ultrasonic sensor. The processor is
A periodic component detector for detecting a periodic component of the ultrasonic wave detected by the ultrasonic sensor;
The generation period of the periodic component of the ultrasonic wave detected by the periodic component detection unit is compared with the power supply frequency that is the period of the AC power supplied to the power device, and the generation period of the ultrasonic wave component is determined. A determination unit that determines that a contact failure has occurred if the power source frequency is within a predetermined range or if the generation period of the periodic component of the ultrasonic wave is within a predetermined range that is twice the power source frequency. The contact failure detection device according to claim 7.

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